Automatic telephone exchange



Au 9,1927. l 1,638,578

M. F. HILL AUTOMATIC TELEPHONE EXCHANGE M. F. HILL AUTQMATIG TELEPHONEEXCHANGE Original Filed Sept. 1894 5 Sheets-Sheet 2 JIILZReJJeJ,

Imus/06511 Aug. 9, 1927.

M. F. HILL AUTOMATIC TELEPHONE EXCHANGE original Fileq Sept. 22, 1894 5Sheets-Sheet 5 v K Aug; 9,1927. 1,638,578

M. F. HILL AUTOMATIC TELEPHONE EXCHANGE Original Filed Sept. 22, 1894 5Sheets-Shet g 7 M. F. HILL AUTOMATIC TELEPHONE EXCHANGE Orizinal FiledSept. 22, 1894 5 Sheets Sheet 5 Patented Aug. 9, 1927."

unites 'MYBON rnnrLL, ornate roan, any nsszenore ro wastagennncrarocoiurnnr,

INCORPORATED, es new Yeas, n.3,; aconroaarien or ,nnwronir.

umor/rears raniirrronn EXCHANGE.

Refiled for abandoned application; Serial No 523,852, filed September22, 189 s.

1 Tovember 25, 1922.

Re filed 'for abandoned application Ser. 523,852, filed Sept. 22, 1894:.

The object of my invention is to produce an automatic exchange that willfulfill the tions. I p

of radiating trunk lines running between demands of commercialtelephony. In ac complishing this result T have carefully guarded thesystem against allpossibility or.

interference between subscribers, have simplified the apparatus sothatfit is cheapened and can be easily comprehended and cared for by theordinaryelectrician have reduced the wiring necessary to an exchange and"have increased the speed oi'est-ablishing'connections betweensubscribers I To secure the best results oi my invention the subscribersofthe exchange are divided into groups, each group in a differentlocality; Each group ofisubscribers is pro vided with a switching set,or a set otloop or link connc'cters, adapted to interconnect 'thesubscribers in pairs. By means o'fthis switching set any subscriber in agroup may connect himself with any" other subscriber in his'group. Theswitching" sets of. the

different groups may be interconnected by trunk lines,-a different setof trunk lines between each two switching sets, so

that a subscriber in one group may connect himself with any subscriberinany other group. With this organization the trunk lines may beidentical with those to be described below. This specific organization,however, I do not claim in this patent.

The organization which hpreteri'or thepurposes of'thi'spatent isfollows: The groups oft-subscribers above described are .termed forconvenience groups of the first order. These switching'sets of thegroups of the first order are again divided; into groups, each group ina different locality These groups are termed tor convenience groups ofthe second order. Each group of the f second order is provided with aswitching set or a set of loop or link connecters adapted tointerconnect the various groups of the first order which lie withinthegroups of the second order; A main central station is provided throughwhich the groupsbif the second order may be connected bymeans of trunklines. I

'All subscribers are thus connected wi h one another through one or morecentralsta- In this way the system is made up running i as illustrated"below.

' To use an illu,

tion through the intermediate and sub-cen tral stationsto thesubscribers private lines. Here intermediate station isused'as a convenientterm for tlieswitcl ing sets tr a p line's afford means of connection downward from the mam central sta-fl This application filed I.

group ofthe' second order; and sub-central station is used as, aconvenient term for the. switching sets or a group-of the first order.

in order that the subscribers may secure a connection withthe maincentral station an additional set of trunk'lines is provided f directly;from the sub-central switching sets to the main central station Thesetrunk lines are used in one direction They may be termed for'conyenience short cut? trunklines.-'

It is additionally noted that the trunk "lines between anytwo switchingsets may be from one to a dozen or more according tot'he needsoi thesystem.

The tchingsets of the groups ot the rst order," r,

{the switching setsoi 'the' groupsof thes'ee 0nd order or; asgli hayetermed them; the intermediatestations, may be located at, con venientccntersin these villages, towns, or cities; whilelthe main centralstation may be located-at any convenient-central "point; a county seatfor er; nple.

ti On, ton D1 6., is'connected tion in his ii'i'nnediate locality andthe various sub-central stations in-Jiiclrington are central andintermediate stations.

The different parts o'fi lvashingtom are similarly equipped; Themaincentral station forthe r U V as I have termed them, theiftlbr'C-iil'liilill stations, may be located "atdil? anemia of Beringtov asub-central staconnected to an intermediate station located 7'at some convenient center *in hlcltington." i eorgetown 1s sunilarlyprovided with sub scriber in Eclrington,in order to secure a 1connection with another subscriber in his own groupneeds only toop'eratethe automatic switching set of his own sub-central station. But,to secure a connection with a subscriberv in another groupin a differentlocality of Eckington he must connect "him- ;self by means of a trunkline of his subcentral station to the intermediate station,

thence by means of a'trunk line to the sub central station of the groupinwhich the other subscriber is located, and finally to the lattersprivate line.

y And if the subscriber in Eckington wishes to secure connection with asubscrlber in "Georgetown, he must secure through the switching set ofhis sub-central station a connection'to a trunk line running directly'to "the main central station located near the Patent Office; a secondconnection to a trunk line running from the main central station to rintermediate station 1n Georgetown; a thirdconnection to a trunk linerunning from this'intermediate station to the subcentral station of thegroup in which the Georgetown subscriber is located and finally aconnection tothe private line of the tie sired subscriber. v 7

It is necessary in the system described that the subscribers outfitshall be adequate to the operation of switch apparatus to select any oneof the greatest numberof line circuits of any group; that is, if thereare one hundred subscribers 1n. each sub-central group, and if there areone hundred orless lines from any station, subcentral, intermediate, ormain, and in order to do this he may be provided with what may be calledan automatic signal transmitter or commutaitor by means of which hecantransmitto l any switching set with'which he may be Connected any oneof one hundred different signals in order that the switchin may selectany one of one hundredlines I Another feature, of my invention is theuse of a'plurality of trunk lines between any two stations, whethermain, intermediate,

or sub-central stations, as many asmay be necessary for business, soorganized that no eflortgis required on the part of the subscriber toselect between them.

.These trunk lines are so organized in th system that they maybe used ineither direction between the two switching sets with which they areconnected, except in the one c-asealready cited'where the sub-centralsta- .t1ons are connected directly with the main central station bytrunk lines which may be .used in one direction only, namely, from thesub-central stations tothe main central station.

I do not limitmy invention to use 1n a group system only as it'may beused obviousstation. p

The switching sets referred to of the central stations of the variousorders correspond closely to loop or link or double plug transmitter, orcommutator, as I shall hereafter call it, causesthe other terminal ofthe linkto be connected to the desired subscriber, if he be in the samegroup, otherwise to a trunk line running to some other switching set. II v Touse the previous illustration, if a subscriber in a certainlocality of Eckington starts to connect himself to another subscriber inhis own group, one end of a-link at his sub-central station is connectedto his line. He then works his commutator, thus operating a selectingapparatus in the link so as to connect the other terminal of the link tothe private line of the desired subscriber.

Again, if a subscriber in one locality of Eckington starts to connecthimself to a subscriber in a different locality of Eckington, that is,in a different sub-centralgroup but in the same intermediate group, oneend of a link at his subcentral station is connected" to his line. Hethen workshis commutator, thus opera-ting selecting apparatus of thelink so as to connect the other terminal of the link to a trunkline'running to the intermediate station. As the subscriberstarts tomake the second'signal, one end of a link at the intermediate station isconnected to the trunk line already obtained; Heithen works'hiscommutator for the second signal, thus operating the selecting apparatusof the link at the'intermediate station so as toconnect the otherterminal of the link to a trunk line running to the sub-central group towhich the desired subscriber belongs. Finally as the calling subscriberstarts to signal for a third time, one end of a link at thesubcentralstationof the called subscriber connects itself to the trunkline lastprocured, and as the calling subscriber works his commutatorfor the third signal, a selecting apparatus at the called subscrib erssub-central station operates so as to connect the other terminal ofthelink to the called subscribers private line.

Finally we have to consider the case where a subscriber in Eckingtondesires connection with a subscriber in Georgetown. As the ly with manysubscribers and one central subscriber in Eckingtonstarts to' inake theconnection, one end of a link at his sub-cen-v tral station is connectedto his line. :He then works his commutator for the firstr signal,

thus operating a selectinglapparatus in the link so as to connect theother terminal of the'link to a trunk line running directly to the maincentral station. As' heistarts'v to trunk line already obtained. He thenworks make the secondsigna'l, one end'of a link at the main centralstation 13 connected to the his commutator for the second signal, thusoperating the selecting apparatus in the link at the main'centra'lstation so as to connect the other terminal of the link to a trunk linerunning to the intermediate station in" Georgetown, that is, to thegroupofthe'sece 0nd order to which the breorgetown subs 'scriber belongs. -Asthe calling subscriber startsto' make the third signal, one end of alink in the switching set attheintermediate fstation in Georgetownisconnected to the] trunk line 'lastohtained. "He then workshis at theintermediate station so as to connect" commutator t'orithe thirdsignahthusop erating the selecting apparatus in the link;

the other terminal of the linkto a trunk line runningto the sub-centralstation-of the group of the first order to which-the George townsubscriber belonged. Finally, as the calling subscriber starts to makethe fourth signal, one end ofa link 'altthesub-central stationinGeorgetownisconnected to the "trunk last obtained; He then works hisvcommutator.for the fourth signal, thus operating the selectingapparatus of the link' at the Georgetown sub-central station so as toconnect the other terminal of the link to the private line of thedesiredjsubscribe'r'.s

identical; And they'icooperate with the various subscribers commutators-1n the same 7 Each link contains four parts, the receiving circuitcloser,.the circuitcontroller, the

selector, and the transmitting circuit closer ,The receiving circuitclosertorins an auto matic connection between one-end otjits link andthe calling line. In this vay the receiving circuit closer corresponds.closely to the plug of almk in manual systems 'which isinserted intothe'line ot the calloperator in selectingthe line called from a largenumber represented at her board. 1

. group, each receiving iclosr" The subscriber-s commutator t hi Sub?Station when St s' t0 n 'a-Isignal for.

w The links-o1 all the switching sets are Each receiving I andtransmitting circuit closer plays over a switch board at each of" whichswitchboards iswilocated a line ter-I minal-adapted to be connected-tosaid circuit closers. So that in" a systein-"otsgroups I containing onhundred or'. less lines pen and transmitting switchboard co'nta'insltheline ofthegroup. A V 1 "At the receiving switchboard the receiv- Telterminals of .each

ing circuit closer attaches itself to a call-j,

'ing line, 5 and at the -Jtr'ans1hitting.switch boa-rd the-transmittingcircuit closerconnectsgitself to :the called line, These two Icircuitclosersare connected together by two wires forming a metalliccircuit. v Each circuitrcloser has two terminals adapted to] be 7connected to two correspond ng line ter:

minals at its switchboard. A separate switchboard is provided for eachwcircuita connection"operatesja circuitrwhich in turn operates areceiving circuitfcloser'fcausing it"toclo'se a connection with oneendZotits link to the calling line. Then the-commutator'sends in its signalwhich operateszboth the controller and selector, and these in turn causeth'e't-ransmitting circuit closer-of the lmkj. to connect the linkto-itheoalled line, i

and then to; send outaappropriate .,signals indicating the fact, and:linally to leavev the i V circuit thus established read-y tori-converseIf the transmitting erminal hasibeen connected to a trunk line insteadof-to asubscriber directly, the circuit established is the commutatorwhich causes a similar operation of another llnk' ttt thenext switchmgset to; which they trunk line sconnected, A

p The circuit controller' like the usual cord; "SWltClT- loops a callgenerator mto an established circuit to.call the cal-led subsCriber, andthen switches the generatorsoutcf.the

circuit again. I The length of thiscall is more or less1rregular,"varying betweenfone and four seconds n length. This 1 call;besides 5 calling the wanted subscriber also informs the callingsubscriber that his s gnals" 'liave secured the .desired connection.IiUmstead of signalling for a subscriber direct, thecall-' ingsubscriber signals fora trunk connection,

the generator operates the calling' subscribers bells only indicating.to himthat the "ready for ,-a,repetition oftheoperation of v H virus-1iio trunk "line connection hasbeen secured and. that the line isreadytor-another operation of the commutator; y

If the-"called subscriber is sought for tliroughany link, and if he isbusy with'sorne other connectiomthe link tails to establish theconnection with him,*and the' controller does not loop the generatorinto the circuit. Hence the oalhng :subscriberv knows byzthe absence ofany returnsignal that the man ;he isafter' is 'busyand cannot'besecured. By waiting a few moments, 1f the latter 1S throngh with hisother connection, the'desired connection is established and the calls toboth subscribers indicating the at the end of; some predetermined period7 I time limit is intended to guard against any "failureofeithersubscriber sendlng in a dis connecting signalwhen he is throughtalk- .v fling, alsoto guard against an undue prolongation of hisconnection oryother abuse.

fKThe circuit controller alsov introduces a lish otherconnections.

restoring circuit inte connection with the [conversation circuit bymeans of which either "or bothsubsc ribers may restore the linkapparatus to normalconditionready toestab- It consists further 1n]economi-zing operat;

:ing power, and in devices which operate ightly,-eas1ly, certainly andrapidly. Other teaturesare moreparticularly pointed out in-the claims. V

' In the drawings Figure 1. represents in diagram view, the subscribershis subscriberfs station.- 1

Figure Q represents in diagram. view, the connections for "eachsubscriber at central stationto'the terminal switches.

Figureifi 'jshows in detailla cross section v. -f' one of the' recelv ngterminal switch boards, showingthe connections to a set of contactsthereon. I

, Figure 3'shows in diagram,.tl1eselector and circuitcontroller andotherapparatus p v 1 lie clrcuit is also connected through the'com-v mutatorwhen vin'a position of rest by contact springs and 8 resting upon, theplate for each automatic link.

" nections 'of'a trunk line or of aisecond'subof the said A {the'selector.

scriber to the terminal switches.- 'Figureo represents'a continuationiofthe trunkgl-ine' shown in Figure 4 and its ter mina'ls at second centralstation Figure 6 shows=1n perspectlvepart of the"- A-porti'onof amodified form of my selector. .Figure 7 shows part oi -the B-port o-n ofiFigure -8:show s aisectional viewrof apart '-portion with electricalconnections.

Figure 9 shows the arrangementofgroups 0fsubscriberssub-central stationsaround intermediate central" stations, and main cen-" tral'stationspermitting many subscribers; a million or more if necessary,tobeconnected Fig. 10 shows the form of escapement I this. system, I ishow how apparatus at thecircuit of a is open at this point.

' two branches -h and it.

it point 719 normally connected with the switch beconnected through onesub-central station; likewise how one hundred sub-central sta- .tionsareconnected to a second central station. I even showfhow one hundredsecond centrals might be connected to a third central, thus permittingone million subscribers. to :be arranged in the system. I would "not,however, be understood aslhmitlng this higher centrals, torletters orany other charactersmight be used to designate their relation tothesystem. it system arranged upon the; basis of hundreds seems however, tobe preferable, as it strikes amean between unnecessary operations onthepa-rt of calling] ,sub'scribersand unnecessarycomplication ofinstruments;av

1 Each subscriber is providedwith'the ordinary transmitter, receiver,magneto it so desired and'bellsused in the present outfit. In additionto this outfit he is provided with a circuit changer or commutator andakey board. a central exchange-to electro-magnetic de- Vices throughwhich he is enabledto obtain connection with any other desiredsubscriber in the system. (The side orf the metallic cir cuit a isconnected through contact points' am and my, adapted tobe opened uponthe operation of the magneto mg; From thence, the side a of the metalliccircuit is connectedto the switch lever S The side a oifthe metals.VVheneverthe commutator is in motion side '6 of the .metallic circuit isconnected to The branch 7: conta ns the transmitter Tr and the receiverlte and termlnates inthe contact point 71* normally out of connectionwith the switch lever. -The other branch it contains the sig- Heisco-nnected by wires a and b of na-l bells st and has two sub-branches72F and The branch ,h terminatesin a. contact lever S Theotherjsub-branch 7&3 contains themagneto mg normally on open. circuit,

When the magneto is operated the contactspringrcmleaves the,contact'point' (my due ,to the lon itudinal movement of the'ma LD bneto arboryand the arbor makes contact by cm, completing the; circuitfrom wire Z) through the signal bell si in the branch h 7 t0. the Wireact the metallic circuit, permitthe earth E.

apparatus in casethe automatic call, which is sent out from central,fails to bring the called subscriber to his telophone/ Inthe branch k isa contact lever L adapted, when the receiver is hung upon its hook, tobe forced by its switch lever S into contactwith the point L" which isconnected by wire L to V] hen, :however, the rece ver isremo ved fromthe hook, the lever L vis forced 1n the opposite direction and no con- Imaybe adapted to tact is elfected. In either'case the insulated end ofthe switch lever S is so shortenedv as to permit the contact lever L topassto the other side thereof. The details of this circuit closer arenot necessary to an understanding of its function, The organization 1 ofthe subscribers commutator is as follows:

The metallic circuit is branched by 7 two wires 8 and s terminatlng incontact springs connecting oneside or the other to the cona ductingstrips of the commutator. The strip a has branch strips 8 On oppositeportions ofthe commutator, I arrange contact springs s and s of akeyboard S. The length of the branch strips 8 on the circuit changer isso arranged that the. contact springs s or s have their connections tocontact springs s or 8 completed av'ariable number of times; In thedrawing, as arranged, the left hand contact spring stand the left handcontact spring 8 are electri-" cally connected to the contact springs sor s ten times, the next one of each series has its circuit completednine times, the next eight and so on until the last spring ineach sethas its circuit completedbut once. The number of variations in circuitconnections the organization of the system. i

I have shown a plug P connected 'by wire p to the earth at E. f Thisplug P has trans verse slots '77 permitting the jplug' to close thecircuit from the ground to the cross strips -8 or s atany junction.Thus, by;

' placing the. plug over the lefthand contact strip 8 and the topcontact strip 8; the right hand contact spring 8 of the circuit changer,and the right hand contact springs of the circuit changer are ground-edthrough the v plug. 1- preferably use a special button at each junction,the button when pressedm'aking contact with the cross strips and ground,The top rod 8 and left hand rod s are a permanently grounded by the 7wire 5 so that whenever the commutator is rotated it completes a circuitoverthe wires a and 6 once. This, as will be more clearly described,establishes connection, ,Wlth a trunk line. When the commutator rotates,

the side b of'the'metallic circuit is grounded over thefollowing path:wire Z2,"branch's contact spring s ,,strip',s branch strips 3 of thecommutator, right hand contact sprmg 8 to the unct1on O of the keyboard,

avire 5?, and the earth E. This circuit is completed on"ce,i-that is,the wire l) v is grounded" at fthe subscribers. station once. After thecontact strips 3 and s have all passed beneath and beyond the contactsprings s and 42?, they create new circuit f connections through springsand 5 so that the side-a, of the metallic circuitisgrounded as follows:wire a, branch 8?, contact spring s strips 8 and 8 right keyboard, wire8 to, earth at E; In

junction l thad been selected and the plug so hand spring s 'to' thejunction O,"of the this manner wire a; is grounded also once; If

of they metallic-circuit would have been vgrounded twoftim'es and thewire w ofthe' metallic circuitjwould have been grounded live' ti1nes;the circuit in these cases passing through plug P to earth at'fE, inlike man-v ner if junction numberedf43 had been se lected" wire I) wouldhave been grounded" five timesfand wiredizr four times making ninecircuit connections 1 at successive periods of time Twenty is the h1gliest number of circuit connections thatis necessary when one hundredsubscribersare connected to one sub-central exchange; This number wouldbe varied according to the immber of subscribers'in the group. Slight"changes in the circuit controller at central would permit a greatermaximum number of connections to ground if desired.

The operating device forthe commutator,

is constructed as :follows. To a buttons is rigidly attached a rack sin,1nesh with 7 a pinion s? rigidly mounted on an arbor 8 the endyof:WVhlCh'lS squared sothat a clutch 9 will freely slide longitudinally]thereon, but will rotate always with I'the arbor. The other part of theclutch s 9i -i's rigid with the "commutator, {which is loosely mountedon said arbor so that it willf-reely f rotate thereon. A springs holdsthe" two" parts of the clutch pressing against each other; AQ SPllDg Spulls the rack down:

8' holds the "rack and commutator in its ,7 i

normal position VVh-en therackl is operated againstthe force of thestoutspringfs it turns the pinion, which turns thearbor and the lefthand part of the clutch 8 the other part 'of the' clutch and thecommutatorgre m'aining stationary. When the pinion and clutchandcommutator begin to rotate; An escapement, shown in Figure 10 is rigidlyattached to. thecommutator to regulate-its 3 speed in rotatingf Suitablesupports are provided for all'parts. It is to be understoo'd thata'ny'other apparatus accomplishing the same function, electricallyspeaking,

performed' by the apparatus shown might be substituted for it. As thecommutator begins its rotation, the circuit oftheline wires is broken bythe conductmg iece s on the commutator passing away from the x wirea,contacts R8? of the restoring button, wire a, brush 8 brush 8", magnet.Mr,

I ing purposes.

fifbe substituted for the 'ground, but this s unnecessary. 1

:draws the vdetent.

thence over the rest of wire 8 to earth at E; This circuit would be madeand broken were it notthat the wired was grounded through a batterycentral, and the local magnet M9" was energized; attracting its armatures thus'placing the detent roller 8 in the path of the stop on the rearside of th'efcommutator, holding the conimutator. from further rotation'When the circuit ofthe line wire .aiisbroken at central from thebattery, as Wlll be described, the. detent-releases the commutator whichreturns to normal positionunder the imp ulsion' of springgs making anycircuit ch'angesthat the keyboard may determ ne. Breaking the circuit atRs? will also release the. commutatorin case an error has been made andthe commutator, has not been released from the central station. Inreleasing the commutator the spring 8 with- VVhen the commutator is inits normal position as shown in Figure. 1, the .circmt of the line wiresis closed through the brushes 5?, and 8 9 and plate 5". Dr'rrmg therotation of the commutator this circuit is broken, thus splitting thecircuit, so that either side maybe used on a grounded circuitindependently of the other, for operat- A third wire may of. course i"The roller may b eomittedifrom the detent and the end of thesamerounded oh smooth, and the spring may be omitted if the stop 8presentsan inclinedsurface to i the rounded detent, sufiicient .toforcethe detent outof itspath when not operated by the magnet.

Operating the subscribers instrument in this manner is followedbycertain electrof' magnetic'action' at the centra-l station, To describethis action is thenext b ect. F gure 2 represents the apparatus at thecentral station to which he directly co nfnected In this figure thewires and b are the linew reswhich come from-I the sub 'scribers stationconnecting him to the central statlon to which I refer. The apparatus'inthis figure is shown in itsnormal posi- Eac himself circuit closers aremounted upon one arbor brushes Z2 and 5 and the line wire a is.

grounded through magnet Mr as follows ink is pji oviaecl', 'se Figures2, 4,

and 5 with receiving circuit closers Rs and transmitting circuit-closersTs, one of each for each link. By means of these switchesa subscriber isenabled toobtain the use .of central connecting devices and to connectwith another subscriber. vMany to the movable contacts on the arm U ofthe pairs of contacts 1, Z Z Z, respectively. The stationary contactofthe' pair Z is electrically connected to the brush Z This brush passessuccessively over one of the insulatedv contacts of eachset of con.-tacts around the frame U and is shown in Figure 2 as resting on contactof sub scriber No. 92. Tn'Figure 4: this brush is shown resting oncontact Tt belonging to the set of contacts of thetrunk line T. InFigure 2 the contacts t are connected to branches of local circuit iwhich supplies battery power to the switch for operating purposes, fromdynamos or battery D shown in broken lines in this figure, but being thesame battery as D in Figure 4E. r

The stationary contact of the pair 71 is connected to a brush Z whichpasses over a separate contact in each set of'contacts on the switchboard, shown in Figures 2, 2 and at as e This contact "is connected tothe branch \viresa of the respective operating circuit. 7 commutator bypressing. the button 8 for operationand the commutator is detained bythe armature s, the line a is grounded over .the following circuit;grounded source D; 25 (see also Fig. 3) circuit breaker a magnet Mt wire6 line wire a, normally closed circuit breaker RS wire s -fl'contacts '8and s, magnet M1, ground at The magnet- M6 .closes the operating circuitat 11, as follows: battery D. wire 25 contacts 23*, wire Contact Z brushZ contacts Z,

On the lever is an armature m adapt- This So that when the subscribersets his p magnet M contacts Z brush Z, branch wire n wire 14, contactsa wire u, contacts a wire 5' to the other pole of the battery D.

which first passes" onto the subscribers row of contacts upon any of theswitch boards R3, the switch arms or levers U. of the different switchboards being normally located at different radial positions around theshaft, which drives them. This operation breaks This circuit actuatesthe tilting lever U the "commutator o 7 single rotation. Before itsinertia has permitted' it to ground the line wires any further, thetilting lever has completed the circuit through the switchboard to theselecta ing and other apparatus of the link as follows: The line wireais connected by branch a and its contact, through the doublebrush Z ringcontact Z side La of the metallic link, and-further normally openconnections described in connection with'Figure 3/ y The line wire?) isconnected through branch and contact 6, contact ring Z to the side L?)of the metallic link, to ,iturther connections shown in Figure 3. Thecontact rings Z and Z are common each to all the sets of contacts on theswitch board. lVhen the tilting lever U has assumed its operativeposition it establishes new and retaining local ,cir-

cuits, and breaks'the operating circuits of th sfcommun cating line toall the links.

.For example the contac'tsl and Z are closed,

and the following circuits established.- Source of electricity D, wire imagn'et Mt, wire 6 branch t? and. its respective contacts on the switchboard trame; brush Z cntacts Z magnet M contacts Z brush Z normallyclosed (see Figure 8) circuit controlling wires i connected to ringcontacts t, thence by brush Z to a contact connected to one of thebranch wires 1) of wire 11, thence to magnet Mo, wire 6 battery D. Thiscircuit contains thetwo' magnets Mt'and Mo,

which break the operating circuits to, a, and v t by which thissubscriberobtains' the corn nection to any link. Since theseoperatingcircuits are -broken after the operation of one receiving circuit closeras described, it

follows that no other circuit closer switch can be operated'b'y the sameline. In other I words, the subscriber obtains f connectionautomatically and exclusively with any one of a number-of links thatmaybe idle and in order. It 'is'noted that each communicating line a,bps-connected by branches to'each' receiving, switch board of the groupto which he belongs and hence he has contacts'on each switch board Rsshown in Figures fl, and 5, as well as in F1gure 2. I have deemed itunnecessary to showthese connections as a differ-subsect ons oi" theswitch board would have to be illustrated, andit would be mereduplication. must be noted also that there is a separate circuit mu, tand 25 for.

each set of contact points on the switch board, orin other words, foreach communieating line. But these circuits for a given connected to theother end'of oneoi'the links, mayobtain connection with anothersubscriber; F or example, a person connected to Rs, Figure 4-, 1nayobtain connection with subscriber No.= 92 whose COIlIleCtlODS are shownin Figure: 2. The linewires a, b of this subscriber are connected bybranch wires and contacts a andI Z)? toeach switch board of the switchesTs. hese switches are very much like the, receiving switches Rs, exceptthat they have less parts, and simpler cir cuits. The operating circuitmaybe traced as follows :"wire 6 which 1 branches from the link selectorAB, and to'which a source of power 1s connected by the callinSUlJSCIIbGl,

a I D I as described more speclficallyc hereinafter, contact on theswitch board connected to wire 6 l), ofthe 'i'rameof thefswitch boardsT3, the first brushZ that comes into 'tacts Z now closed, brush Z branchof of wire 4), magnet Mawire t battery Dv This magne'tbr'eaks theoperating circuit '11,,-

so that atter thisaction'ot' one transmitting 'ci'rcuit closer no'othertransmitting circuit closer can be operated at the same point in itsrotation. In other words, whenonev subscriben has been connected toa'-link no other person; through the same or through another link, canconnection withhim.

The "stationary contacts of the pairs Z,

Z Z Z are in lpract'ice as those shown in loo the diagram, yielding oisliding contact sprlngs, soithat the retaining circu'itis, al-

ways completed before the operating circuit is broken, so that duringthe' transfer' of circuits, electricity is flowing through I the magnetMThe diagram view shown is su'tiicientior this case.

A' morc detailed "description a nd'illustra tion ofthe-switcl'i boards"is'not deemed necessary,;a s they are broadly similar 'to those wellknown in the art 'of 'automat'ic '7- exchange systems, ands sectionalview ot the frames showingmy inventionis suifidynamo or battery D. ThesideL?) or the d link is connected by branch c'through the circuitcontroller; to other :operating. mag

.troller C0 'tomagnetxM? and thence to a" nets. 7 From the line wireLbthe branch 0 I runs through contact SP1lIlgS-,,6'O, resting normallyupon contact. plate of the circuit controller, thence by 'wire ct tothemagnet M thence by the same circuit 'c point 03 I connected to one poleof a source" of electricity I), which is preferably either a chemicalbattery or :a dynamo current according to thesize of the'exchange. Theother pole of'the battery is grounded as shown at E. "A dynamo may beplaced at one central point and furnish power to all the centralstations of the exchange, the

other pole grounded at the dynamo. I might, instead of using fthisdynamo current, use chemical batteries or any other i source ofelectricity of a nature to operate electromagnetic devices.

By this arrangement Iefiect a great saving inthe cost of 7 operating theautomatic exchange.

Vhen the line wire 6 is grounded by the subscriber for the first timeupon the opera-.

' Ltion' of the commutator, a circuit is found from theground at Ethrough the dynamo *D, thence to point d over the circuit 0 and 0' astraced, includingmag-net MT, thence to linkwire-Lb and-line wire 6 to.ground at subscribers station. A parallel circuit,

magnet M is energized itattractsthe armature m causing the switch Q toleave con- 1 tact point connected to wire 9 upon which it normallyrests, thus breaking the restoring circuits to adjust the '40 throughthem, as it vis desirable, though not circuit during connectingoperations.

Ree sistances may be interposed in any of the currentflowlng at alltimesnecessarypto have circuits of V substantially equal resistance;

IWe have followed out the consequences of the operationof magnet 'Mhbutwe have not yet followed out-the consequences of the operation of themagnet M. This magnet,

whenenergiz'ed by this first impulse open ates the circuitcloser mbefore referred to,

l 1 closing the local circuit m? from pole n of battery D," throughmagnet M as follows:

battery D. circult closer M wire g magnet M ,-circuit breaker d openduring res- .torationycircuit 0 to pole n ofbattery'D;

magnet lVt attracts-armature m thereby operating the ratchet. and pawlmechanism 1 which rotates the circuit controller C0. The

contact plate imay pass away from the contact spring- 60, breaking thecircuit which has heretofore beencompleted to 6 at the first step of'theratchet r 'Theucontact plates i i 6*, and-i are brought beneath thecontact springse 6 e and e ,'c0mpleting circuits thereby.

When the contact plate 710 breaks the circult through the. contact e and60, circuit the first.

of a number of rows of contacts of primary 0 is cut ofl' from thelink'wire Lb-so that no later impulse will keep the restoring circuitbroken that may be intended toclose such circuit.

In each link I employ a selector to enable any subscriber "to select anyone of a large] Or to put it in another way-,- a number of in' sulatedelectrical conductors adapted to be operated over rows of contacts,eachconductor over a ditl'erent row, and'a common mo tive' power for all ofsaid conductors, and a second motive power adapted to establish-I acircuit through one of said conductors to the exclusion of the others.In my selector construction I prefer to have the switch arms make actualcontact with each of the contacts in its'row, and a separate switch armto make connection with one of said first mentioned switch arms therebyestablishing a circuit through it. But it is obvious that many changesmay be wrought in the actual construction and method of operation.

It is obvious that a single motivepower may operate one part oftheselector,and then be adapted to operate the other and not The primarypart A is composed order rigidly fastened to a support. I have shown tenof them in Flgure 6; on each row is a number of contact plates, eachplate being the terminal of a diiferentbranch line. I have shown elevencontact plates on'each row but thefirst contact-plate on all the rows isa dummy on which the contact arms normally rest. tact arm 72 rigidlyconnected 'to an arbor so that as "the arbor rotates all of the contactarms make contact simultaneously with Over each row plays a con-;

TO i

contact plates upon their respective rows.

The arbor isoperated by suitable ratchet and pawl mechanism andby magnetM The contact arms 6 are insulated from each other and each iselectrically connected with a different contact plate on the dial or.row of contacts B of primary order.

Over this row B a contact arm' 6 is adapted to pass, operated by aratchet'and pawl device, actuated by magnet M Connected with the arm 12is the line 6 which it is desired torbe put in electrical connectionwith any one of the contact plates of the instrument A h withthe-contact arm of the instrument A' T was??? from the wire lettered b-to contact-arm l)- to thecontact plate b v to thewire b to the contact6 to the seleetedcontact plate 5 and branchwire be. In theinstrument Athere are shown ten rows .of' contacts,,eachhavingeleven contact plates,tenof which. have branch wires; making in all one-hun: andthus put inconnection through itsapprodred contact plates forelectrical connection.

This number maybe varied at will, but this:

system being planned for one hundred subscribers, I have preferably"shown one hundred contact plates by means of which the subscriber isenabled to obtain connection with any other subscriber belonging to hisgroup. On the first row/of contacts the second contact plate lettered btand .corre- .sponding to character or Ms'on thejsubr 'scrib'ers keyboard does not represent a subscriber, but represents any one of anumber of trunk lines to a central stat1on..yA

, line]; leads from this contact plate and has branches b" leading eachto a contact seg-' ment of av different set .ofcontacts on thetransmitting switches TS so that when elecsubscriber. No. .19. Onthegthird row the last contact plate represents subscriber-No.

tricity is supplied through the selector .to these contacts, the firstone reached by the switch arm will. cause a connection to be establishedto the; particular trunk .ine it represents. The switch armonce operatedcannot connect to another] set ofline tei minals. The third .Ilc-ontactplate on the first row ,represents' subscriber. No. 1;; the fourthcontact plate represents subscriber No. ,2;

scriber No. 9. Onthe second row the first contact plateis a dummy thesecond contact;

plate represents subscriber No. .10g0f, the

29. Inthis way the first row contains 'contact plates representing,subscribersl 110.9;-

the second row representssubscribers to 19, or represents .thetens, thethird repre-i senting the twenties, and so onupv to one hundred. Thisdetailed description is necessary only to show one of the many=differentarrangements which I contemplate-as possible when using these 'deyices.It is obvious that other i arrangements might be used. i a

In following the operation of the corn-' Inutator ofthe subscriber wehave noticed that the line wire. 72 is grounded atthe 'sub scribersstation a selectednuinber of times; :l/Ve will suppose that subscriberNo, 92 has" placed his plug P upon the junction/1130f the switch board Sash'eretofor'e mentioned. The line wire Z) is then grounded five'tiines.

The first impulse passes over circuits 2, of

etc, as we have seen. i V I H p The subscribers commutatorthroughcontact plate 2",- wire;c,to linkwire Lb, 'linehwire b to groundatqsubscribers station through the commutator and; key board." Themagnet M thus energized ,fiV, times, closes the contacts ml of circuitml? containingn iagnet MP, andthe contact'arm bl 'lS advanced to thesixth contact plate-b ?"v priate wire bt wvitli the fifth contact arm7). I otthe instrumentletteredA; i v p having grounded the line wirebfatv his; stationa ground the; line wirea also a; determined nuniber oftimes. .W hen the line "wirea .g-ro unded,, current from the 1 dynamoone v pole of which is grounded at E as we haye seen, flows by way otvpoint d circuit wire,

. j, magnet M over circuitj. to contact springs;

e yresting afterthe first advance, of the 'con-,

troller Co on contact. plate 2', thenceto the,

line wireja and'lto ground i at subscribers station through his.commutator and key board; This circuit is'completed to ground. by the,sibscribers commutator four times, aswe'have noted, when subscriber No. 43

is being called. This inagnet Mtis therefore energiz'ed four times,"correspondingly,

closing atmzl the'vcircuitf ml from battery1 D, includingmagnet}Ml,advanci.ng all of the'contact arms 6 by means otthe ratchet mechanismtothe fifth contactplate ;on' each row, and circuit connection. isestablished f1om'.,tlie line b v through-the contact arm;

$ contact plate 1b, "appropriate wire 6 fiftlifcontact arm F2 9,- .it'sappropriate contact plate 6 on thejrow ofthe instrument 1 Aand the wlrebe connected to-that-cOntact plate. In the meanwhile othercircuitshave).

troller Cc 'closes'the following intermittent errcurtgbattery D, wire()5, circuit b reaker been. established..,The first step of the'cOu-gv dmagnet'MBlconductorg ,circuitfbreaker cb, thence to contact springs 63resting'on the-f -1 H plate z'i'thencga tolspringse and plate; 71 thenceby conductor 0 to "battery D again at N This circuit. is made andbrokenbyl. x

the-circuit breakerfcb at regular means;

energizing the magnet M atthose. intervals and advancingthe circuitcontroller step by iv step, thus, taking it beyond thet'contr'ol 0tthesubscriber unless he grounds his restoring circuit ashereinafter.more.fully' de scribed. This-circuit breaker may be drivenby aniotor either directly gearedthereto. or, may be operated by a clockorthe rotating arbor Ts, or'in any way that suggests itself to i theskilled artisan there being one for each controller. As long asanysubscriber musing the, stationjapparatus, the circuit,

breakeri-cb'is in operation except incase the f timef feature isomitted." Insuch case the levera e plate a is cutoff so that after thesignal has been sent out from CG, the circuitcontroller maintains instatu (1110 the circuits existingiduring connection and stops advancinIar'range it preferablyto close the circuit but once in every threeseconds instead of this arrangement a ratchet with a difierent number.of teeth might be used,

' orthe circuit breakercb might be operated at a differentspeed and thusvary'the time required for-thecircuit controller to make have seen, isprovided with aselector as'AB' I the full revolution.

7 At the'j'first operation 'iof' the circuit com troll'er, contact plated is brought beneath thecontactsprings'6 closingat this point thefollowingcircuit' fromthe battery D foint n circuit wires and npmagnetsand "M to'the twopointswitch Q. 'Ifthe two point switch Q were inits'nor .flmal position. thiscircuitiwould be continuone through wireof, andwire c thence to it 7 batteryD" again. It now the magnet 'Mshould alon'e'operate to retract switch Q, to its-normal positionthereby completing the circuit a. and energizing the magnets l M 'and Mthese magnets would-withdraw the: detents cl, and dpermitting'theinstruments'A, B andCc to return'to normal position, andprovide a slight retardation Qfo'r thecircuit controller, so that itwill not resume its normal position till the other in- V struments are.restorech fThis'i's effected by- I .giving Gc, some inertia; or anescapement may be used with" goodiesult, or another retardation device.I have not shown. and

'do 110t deem it necess ai'yto' show the details of myratchet and pawlmechanism, but I prefer to use the ratchet and pawlshown in the patentto G. L. Anders, N0. 2 l0,878',

- .dateMay 3,1881, which holds the pawl norm'ally' out fojt'engagcmentvwith' the; ratchet fbu't. .forcesit into engagement with theratchet when'operated and locks the ratchet" from-further advance whenthe pawl has finished the length of its stroke. This re storing-circuitmay be closedfor operation "timeatter the. contact plate 2'? has at" anpassed beneath the contact springs 6 so that "if the subscriber makes amistake in' calling up" another subscriber, or for other reasons 1desires not to prosecute: his connection, he

may at 'once restore all his central office de- Y vicesto their-"normalposition. I These restoring devices will be more fully referredtojhereinafter. 'As the circuit controller con "-tinues 'to rotate.under the influence of the magnetM the circuit'throughthe contactsprings e a'nde and contact plates 2" and f? are broken, the followinggrounding 0f theline Wires a or b will have no effectupon 'the'centraloffice connecting apparatus operated at this point. Vvhateverq'oc'cursafter these circuits arebroken is due to local circuits. When thecircuit controller brings the contact plate *5 under the contact springse electricity from-the dynamo D- isthrown over the following circuit hempoint a,

plateb and branch wire be.

Before following out the effects of'this circuit, more additionalexplanation for the plan of connection otthe various central instrumentsis necessary. Each link as we and two terminal circuitclosers R5 and T8respectively. From each selector to each set" of contacts on thetransmitting switchboard T8; so that by means of these wires-6t" of 4the-selectorany subscriber who has obtained, the use may by connecting'asource of clec-" piece Z) andthe contact brush Z of the t terminalcircuit closer-Ts, the magnet M The circuit wouldthen beiiromdyna-nio I), point 7?, wire 0, springs e v'and plated olthe circuitcontroller Co ma gnet M wire '6 'tricity thereto, control throughthejconta-ct inn 7 through selector A, B, through branch wire b't shownin Figure3, andshown in Figure" l, to the switch board Ts of thelink}through contact plate b and the brush Z of the ter minal circuitcloser Ts" to the magnet M thence to the normally, closed pair of contacts Z to another brush 5? connected thereto,

onthe contact arm of the 'circuit clos'er Ta,

solated from the first brush, thence by conf tact plate at on the switchboard and wire a, circuit breakers u ccfi, to t, "battery D. This magnetM will attractits armaturem closing the. circuit between the link and.the trunkline as will shortlybe described. 7' The plate b may be commonto all the group of trunk lines running between the 'switch and oneother receiving switch, or separated, and each segment conne-ctedto abranch 72 of wire btfi. The contact plates I of the subscribers sets,vare j insulated and indcpendently connected to the selector plates. Fromeach subscribers or trunk line wires, 7

' run branches lettered a and 5 to contact] pieces in the set of thissubscriber on the frame of each transmitting switch board of thegroup,through which the saidline is adapted to be placed in connection. Thesecontacts form part of cachet the sets of: ccnvtacts around the frame ofeach switch board.

The lines eachf' havei cbntactpieces a b upon th'e different swi'tch=boards of the transmitting terminal'switches' and thus the branches aand b are adapted to be placed in connection w1th'the'lnik wires ofany'llnk.

The current from'battery D is sent through circuit closer from making.connectionwith thisline. There: is a separate magnet M1) and-separateoperatingand reta ning c1rfcuits andcontacts therefoe for eachcoinmunicating line. The operation of theterminal circuit closer T8 isnecessary to the final completionofa through talking circuit from acalling Subscrxbento called subscriber and such a' circuitcontains buttwo breaks at central, both closed by magnets M The contacts obtainedatFeach break in the talking circuitare thusretainedlclosed byimagnetic'attractiom and in practice this is found superior to spring jackcontacts. When this switch operates, the magnet M closes the circuit-forthe'controller magnet M as-foll0ws,battery D pole' n Wire c contacts onclosed-by ma 'net M wwire 0 a a V, brushes 6, plate 2 circuit breaker0b,,w1re g magnet M (5*, wire c rrandwbattery D intermittently advancingthe controller as a wires '7' and 0' contact springse, plate 77 of thecontroller; thence to the other pole of the generator CG. This'generator may de 'velop either a director an ialternating currentasdesired as long as -1t will operate the bell of a subscrlbers outfit.yByextending the plates i and 77 of the controller, and using retardationcoils to're nd er the current inaudible, and prevent interferencebetween two or more conversation circuits,this cur-a rent may act as abasis for thespeaking current. In such acase the subscribersbells' wouldcontinueto ring-until the subscriber cuts them out of" the circuit athis station.

hen an alternating: current is developed 1 by this generator CG; Iprefer to'tone it.'

hen the link is being'operated with sub- "scriber. Yo. 92; with; whom weare dealing,

the circuit isclosed through both sidessof fthe link circuit, asdescribed, over the .line

wires a andibxleading :to the station appara;

. trol of central switching" apparatus. And

switching apparatusconnected thereto are automatic-ringingof bells maybeonto and: the magneto used entirely}: -;-The tr'i tus' shown'inflFigurel When-this occurs. a the circuit is completed-and thecurrent from themagneto generatorWillpass over both limbs of the metallic circuitringing the bells onsubscrib er No. 192s line informing. him that thecircuit to thetrunkline'is completeand ready for the next operation ofthe com mutator. This is on thesupposition that subscriber No. 92fisobtaining. connectionfwitli a trunk line Ta; Tb.- If instead of selectlle mg a trunk-line he had selected-a subscrib ers line No. L2 inbroken, lines in Figure 5,1 the bells of that subscriber would have beenI rung also informing him thatl'ie was wanted at the telephone, at thesame time,-th at'-sub-' scrlber No. 92 received hisv return" signal. Theabsence of a return signal to the opera ing subscriber informs himthat-the desired person is busy, or that the accommodations of switchingdevices proyided by the-company are insufiicient -fAnd if he hears thecommutatorof his outfitoperate, he knows that he has obtained possessionof-switch ing apparatus. So-that thevoperationof the commutator"accompanied by 110 bell signalwill indicate that thedesiredfline is:busy. And absence of'the commutators operation indicates an inabilityof the line to'g'et con-i when the 'coiuumtator is?setQfor-toperation itWlll remain ,there till it gets: connectiondto central, thecallremaining some. The

link switching" apparatus-will inake a re spondingconnection atj'anytime before i it, is restored.) So that'zifa" desired subscriber isbusy; the calling person, may, by wai-tinef, get connection withhimtheminute he gets through.

' 'VVhen a 'subscribers {circuit andthef link restored, 'the magneto'signaling..current is again sent outbymeans of detent (Z which'closesthe contacts 'cl andd of the magneto CG to linkiwires :LaandLbover the line momentarily notifying thesubscriijbcr of th fact; ifheis immediately called agai calling: signal'zis distinguished by itsmtg-111 If, n0w',-the'called'subscriber doeshnot an:-

slwer this signal; subscriber No. 92-,may; as

shown in Figure '1', turn the crank-cit his magnetovmg sending a currentoverhis circuit again ringing the bells of the called subscriber. Inthisway; the calling: sub-'- scriber may sendadditionalisignals to thetelephone bells of the calledsubscriber if the" latter-does not answerthe first signal which} 3 i as described, is automatic. have ishjown"the. magneto mg jas aypossible arrangement. It may,:howeve1', beentirely omitted from the. subscribers outfitand-:theLcOntacts-am: and(Ly be omitted from the linen-a that the line ma be permanentlyconnected to the switch lever 5011* the. other hen h 2 I line isunaffected b the ringing current, until another subscri er 1s 1n thecircuit.

I. have referred: to-a restoring device whereby thesubscriber may'at anytime after he has'sent in his first impulse, restore .allhis'instruments'to their normal condi- 'Ition. Also howjthes'e]instruments may berestored at the end ofqanypredetermined time and allconnections with. other; circuits be cut. off. I It is now my purpose todescribe I these; devices. There are a number of dif-l ferentarrangements which I have contemplated. I might provide avthird wirerunning from the subscribers station to the centralstation, to which heis connected, and h' magnet M to battery, thence 33y grounding-thisthird wire storing circuit 1 at this point.

I would beclosed through the automatic links to a similar wire ofothersubscrlbers clrcults-or trunk hneclrcuits 1n the same mannected. totheir circuits,

ner, as thetwo line wires a and bare con- The third wire however, Ibelieve to be unnecessary and undesirable.

When the b side of the'metallic circuit including the link wires, isgrounded by a commutator forthe firsttime, we have seen I how it closesthe local circuit for magnets .M'Z? and. MZ by means of relays M and Mparallel between dynamo D and "wire Lb, operating the controller and the,B-por- I :tioriof the selector. ;A third parallel cir-- i cuitis alsoestablished as followsydyna'mo e0, plates'vlo, and f5, brush 8 wire 0,to .link wire L b, thus attracting the restoring switch Q, to its openposition. After thecompletion or the first advance of the circuitcontroller the circuits are altered. The magnet M is cutout by citsparallel circuit) being broken 1 at brush '6 and plate, i and the platei, connectedto plate Vi, brush 6, and link: wire, L5, is connected tobrush 6*, after the controller has completed the signal on thesubscribers bells, and thence by way of wire 9 to the primary coil ofmagnet M, wires 9 to battery D, so that as often as the side 6 of themetallic circuit is grounded a part of the current from battery .D willpass 1 through it and attempt toattract J switch Q to its closedposition which is noranal. A secondary coilmaround magnet MY includesanother relay M and ifthe I current in the primary" coil of magnet M I lstoring switch Rs or S 'contactlngwlth is intermittent, induced currentsfromthe secondary'coil energize magn'etM, closing the contacts m causingmagnet M to be energized retaining swltch Q, 1n 1ts open position. "11fthe impulselaststoolong, as'will happen when a subscriber closes h'is reposition.

lever L, the induced impulse in magnetM will die, thecircuitxcloser mwill be broken, the magnet M alone energized, and the switch'Q,restored; .it is essential, that one of the contacts m be a spring inorder that the impulse be long enough to; operate ratchet magnets thuspreventing magnet- M from being deenergized. -VVhen one con- 7 relaybecomes "adapted admirably for the work to which fit is applied. Uponthe adjustment depends thev length of impulse which may be used forthe-ratchet-magnets,

After the strength and or re'laystherefor. momentum of'the relay havebeen fixed, ad dition'alJadjus-tment for impulses of varying length issecured. by adjusting the distance between thespring and'armaturecontactsu A make and breakvofcircuit'b to ground closes these contacts,so that the line wire.

7) may 'be'grounded as oftenas desired for operating additional. ratchetmechanism, and this delay will remain undisturbed in cuit closer isoperated, it operates the switch closing the restoring circuit at thispoint In the normal position of the controller "G0, the restoringcircuitis broken by brushes 6 and plate 73 but after the first step ina'dvance,the controller closes the/circuit at this point the circuitbeing simultaneously- I D, wire a, wire, magnet M wire tossprings brokenby the switch Q,'so the'detents are 7 free'to perform their functionduring oper ation, but are withdrawn when switch. Q, 7

and operating the circuit closer L, as de scribed. When the circuitcontroller is resuming its normal position the a circuit through theselector and v controlling the magnet M of the transmitting switch T8 isbroken,-.and.that switch resumes its normal rotation. The branchrt ofthe retaining circuit t ,'from of theswitches Rs, is

normally closed at contacts 6 controlledby the detent (Z while thebranch i of this circuit 'is normally open through the through i untilthe: circuit controller-is 'springse and plated-of the circuit.controller. When the detent is withdrawn, the cir-' cuit t is broken atx but remains closed. 5

nearly restored to" normal. This is to prevent the receiving circuitcloser Rs from closing. clrcuit to anotherpersons line andoperatlng'before thehnk apparatus is ready But the minute a restoringvcir 9 teaser to receivenew impulses. The plate if is s ad usted that thecircu t closerRs 1s released before therelay circuits are completedtothe link Wires so that if the line wire 7) is kept grounded ll" theperson restoring it has. no

effect on the link whichis seVered therefrom. The ii'esto';'ing circuitis" not; broken 'tures, I have not show, as they vare K familiar tothose skilled in the art. lt is necessary to note also, as" once beforestated, that the pawls operated by the magnetsMZ and Ml and 'lVIE are'normall out of engagement with their rew spective ratchets, flhestop 0prevents the;

at i untilthe'circuit 1, has been broken at t ?.'and long ienough toreleasethe circuit closer RS. ,Thespe ciiic form of ratchets, de tents,brushes, and other mechanical struc deemed ,it. necessary "to controllerI Go from going :t'urther than its normal position. I The contactplaten"? is 'supposettto be in such positionon the circuit controllerthat when it has completed 1 ornearly coln'pletedits rot-tenants platewill be brought under the contact springs; 16 When this'happens thetollowingcii cuit isestablished :Vdynamo D, wire rflcon taining theprimary coil 0t magnet MQ spring 6*, plate plate 7?",in permanentcontactelectrical connectionwith plate-2'7,

ncl at E.-

Current flows from the dynamo through the inet Mtwhose origin-is in thesecondary coil 5 Figure 10.

magnet ll andtemporarily through-magnet M owing to the closingotcontacts 972,- under the influence of an inducedicurrent-in magofmagnet M. hen this induceiicurrent is dead, the contacts-7n opengagain.'.auto-{ matically, the armature dropping therefrom V and: the magnet Malone isiactive, restoring the lever Qto its normal position, withdrawing the various detentstrom the' various ratchets and instruments toreturn to their normal. tionshown in the drawings. ':'When theinstrunients are restored to normal-position the current on branch 7w;operating'aunag net of the transmitting terminal switch Ts,

is cut oil by the springs eand plate i et the circuit controller. Whenthis switch is re leased its heav x heel re-engages W th' 'the collar itand it continues to; rotate with the' arbor. "The circuit controllerreturns to its I 1 than theother'd parts maintaining the restoringcircuit complete at 2" until the selector andcircuits normal positionmore slowl hayc resumed; their-normal position. 'YThis retardation issecured by the of a fan or by 7 other suitable n eansfliltc 'that:"shownn At thesam'e v operatetlthe side of-the metallic link Lb collision on atrunlnline, between two;s u permitting the Various rangement,'trunklines should be separated an escapementfor dash-pot or any timethat the magnet M is tact spring'e wire t to earth at. E. .-Thl.lsg therestoring {circuit and devices lofallilines, trunl; or other link; linescontinuous iwith are operated andtn devices and fcircui L maintaining aconuersation circuit a e. I stored to nornial'position.iTh-isl'does'away with the necessity time circuitfcontrolier ataf-liigher central stationfan lithe} may consequently be reducedfi'n]size; and I I their operating circuit contact-plate cutf'75 I off atapoint to preventthecontroller from" rotatingto a uselessdistance; suclfacase the plates i 2' 2"? audio woul dfbe longer. than and plate i?wouldbelo nitted; Qon; versely, if all'circuits he obtained through a Ihigher central, as}hereinafter referred: t the links at thatcentralnonema be I Over the circuit "establishe d by a link 1 tween twocommunicating linesany sortof, a current be passediwithout disturbing Ithe electrical continuity oft-he lines so that I byany proper means acentral battery be utilized toz-turnishithecurrent for talk? 9 ingjpurposes, as Well known theft-art.

In Figure l an'd in full lines in Flghf 5 have shown trunk I line trunk;line is preferably connectedito a' set Vof te minal contact 1 points oneach ofth'efswit boards Ts -and ligand theonly di'Iference1 I in theirorganization is. thatlf supply cur rent to all the trunk linecontactsblf iof th e trunk line sets connected to a switch board I Ifrom one line bt g or branches b fpiButjini other respects'thesetrunkline co nnections i 9 "correspond closely to a subscribers lineconnections. I I 9.

So'organized a trunk linemayibe used, in either direction; lhisorganization will f not be liable, onunusualcoincidencesto a I scribers;on account 01, a non-interference *c1rcu1t. If, des red to ayoid thisjathose for transmitting j i m pulses I to o t herf-; groups connected tothe transmitting switch-" a d 717 h s 50 .Ir c ivine imp s 7 from other.groups] connected to the recei 'In-ot'her words, :all. connectionstrans; mitting switch boards'at'one'end andfall connections at receivingswitchfboards the, other'end'of each trunk line 1nay; be, cu off.This-organization slightly .redujces the amount of worlr-a-giVennumber-of. trunks i 20 can accommodate. f

I will now; describe howssubscriberjNo';1., may putliimself intoconnection-with anyfi! 'one or the trunk lines-showni'nj FigureA- TI-e.In-Figure- 1 onthe keyboard S, the upperj crossbar andthe:leftjhandlcrossbar sigiare I grounded permanently, .so that as them; mutator S "operates,flas before described without using the-plug,thelindwires (rand; I I Z) eaclrare grounded once, in Figureg wheof ving switches only andrelaysalteredtoc'suit; i 1 f '7 12s; v v

{the lineiwire'o is grounded once the circuit controll'er C-c' isadvanced one notch and 1 V V 'mally closed, wire X,,to vbattery'l)again,

from that point its local "circuit containing magnet "M is closed Qa'jndthe circuit con" itroll'er continues to advance as heretofore described.f At thesame time the magnet M is grounded once 7 bya parallel circuit;

When the line wire @is grounded ithe mag- 1 net M is operatedionce.advancing the 0011- 10 I tact'arm b -to thefirst contact plate?) of=;the instrument A haying a'wire bt connected jtheretosf Shortly acurrent is thrown on to: "the. wireYfl i'connectedto contact arm Z) by.

' the"cir'ci'iit coiitrol'lerCc through springs e,

battery D,

and contactpl'ate 2' from. dynamo or storage In continuing this circuit,the current flows fromcontact arm 5 contact plateibi'wireb, contactplate 5 itsbranch wire bt thence as shown in Figure 4 to the ContactPlates b on the' fraineiof the link terminal circuit closer"Ts operatingit; By thismeans the subscriber may obtain the use 'of-a trunkline toany central station with 7 .Which his central station maybe connectedIn'order that hen a trunk line liasbeen connected to a terminal switchat one end, it

' cannotbe connected by another person at the f other end, I provide,for each trunk line nother-or thirdwire and an individual battingcircuitclo'ser has established connection at one end as at subcentral,no transmit- [ting circuit closer at theothei'. end, as at, main centralcan connect itself thereto; and,

yet any receiving circuit closer may be'con trolled therefrom. Not onlythisb'ut it is impossible for transinitting switches tomaintainconnection. with one trunk line at both" ends. hen one end hasbeen connect- J fedtoa transmitting circuit closer, as in Fig.

.4, the retaining circuit vof that switch, 'con-,

"dilator: o, 'operatesinagnet Mo contained e connected to the trunk lineby the This non-interference trunk circuit. when closed fat the'stationat oneend, shown in r Figift, is in derivedcir'cuit with one side of"-tlie metallic circuit T65 Ifone-of the transmitting circuit closersTsin Fig. 5 operates I first,i t closes-a derived circuit over theother.

side. of the inetallic circuit, Ta, as follows; b'attery D Fig.5wireXfcontacts 1& closed 5 by" magnet Mifi {energized by. the retainingI ery D 'seeFigsf l: ands, and relays and circuit apparatus, wh ch, whena transmit;

circuit. of-the operated switch Ts thence to Wire Ta, to Fig. 4 wireX',contacts ufl nor- Fig. 5. This circuit operates magnet -X, opening thenormally closed contacts M and a, of the operating and retainingcircuits of the transmitting circuit closers at this endof the line.

This third wire X may of course be omitted, likewise magnets X, Mo,'Xand M12 has been described is preferably to. the main central station sothat before a subscriber proceeds to make connections upon his key-.

board corresponding to the number of the subscriber whom he desires tocan, he places himself n communicationwith-the main central by merelyoperating his push rod.

As the non-interference circuit is in de rived circuit with but one sideof the talking and signalling circuit,'when in useyand severed from theother side of the circuit, it has no eifect upon the use of it.

The main use of this non-interference circuit is Where but few trunklines are required between distant points,- to save. wir-' ing. For onecircuit with three Wires that by duplicating the apparatus shown at thecan be used either way is better than two sub-central, namely, .theautomatic links;

and by repeating'his operating, with his commutator, operatingtheselector and circuit controllers in the various links with which-hemay getconnection and through which he may desire to secure connectionwith another subscriber.

In an exchange of 10,000 subscribers,each

trunk line to the main central'canobtain connection w th a trunk line toany other sub-central connected :thereto. I 'To enable this .to be donesome. trunk lines may be con-- nected toreceiving switch boards at'maincentral, and transmitting terminal switches at the sub-central, andothers have these connectionsreversed, or all trunk lines may beconnected to both switch boards as here- 1n shown; 'And the circuitcontrollers and selectors-of one link central can secure control ofother trunk lines at this point as more fully described later on. Itwill be noted that the subscriber having once. gained connection througha link and a sig-' nal returned to said subscriber indicating to himthat the desired connection from his first operation is completed, thelink devices.

let

' of all the-link circuits with which he may nection with the cross rodslabeled to repre- "sent the trunk lines connected to this iii--grounded, so that by operating his be in connection at that time, totheir nor-f mal position.

If, however, subscriber No. 1 desires connection"with any othersubscriber in hisroup, he needs only to make connection 7' vith thejunction numbered to correspond with that subscriber, obtaining lconnection "-iwithihim directly, or he may gain such con iiectionbyaround trip to central and back, thus obtaining uniformity in his operatons.

This'may be desirable to the more inexperr enced operatory'f Anysubscriber in thisex- Z change may obtain direct connection with centralwithout being, required to perform; the various operations which wouldbe re-g quired if he were compelled to obtain a connection therewith bywayof an intermediate central station. lVhen lower lefthand subscriber1- wishes to obtain connection with lower left hand subscriber 3, Figure9, he places-the plug P upon the junction of the crossbars s ands",shown in Figure 1,-wh'ich are labeled to represent'that subscriber andby operating his commutator, can obtain direct connection with him."This goperation will only answer when he is obtaining connection with asubscriber connected to the s'ub central station to which he isconnected. lVhen, now, the lower left hand subscriber 1 wishes to obtainconnection with another subscriber '1 connected 'tohis'intermediatecentral station, and in describing);v

this operation I describe all the operations 7 [return signal;"Subscriber Not 999,999, by numbers 99-99599, in;

necessary to an exchange'of 10,000 subscribers wherein all thesubscribers are grouped in hundreds, he may make contermediate central.These cross rods I have designated in Figure 1 as permanently puslr'rodthe subscriber will obtain a circuit-through any one of the idle trunklines with which his sub-central station maybe connected to theintermediate central station. From this point if'he wishes subscriberNo,.4 2' hc" grounds the junction labeled 4 and operates his commutatorpush rod; and upon'the re ception' of hisreturn signal indicating "thedesired) connection, he places the plug 1 upon the junction labeled torepresent sub 'scriber 2 and. again operates hiscoininutator; Whenhereceives the return signal he is informed that'the desired connectionis c nreceived is alsoreceivedby the called-subun-t-il.';the "timelimit, set thei'circuit; con

troller has expired, or until. either subscriber' groundsj the L- b sideof the talking circuit; on: either of whichoccasions all 1 of theinstruments andcircuits inzseries will be restored to their normalgpositioni and an additional connection through the link selector AB isprovided tocorrespond witli- 'that junction and the commutator somodified astocomplete a-difler'ent combina .tion of circuit connectionsto suit, orjI may run one or the circuit connections be," whichfinayg'run -ina system of10,OOO subscribers totheterminal contacts of' a"subscriber in the' group, to the proper setsof contact. p oiiits "uponthe switch board representing an additional set of trunk lines reachingthrough to themaiii. 'centralstation for the To obtain connection withanyone of a million subscribers would" 'i'equire four operations onthepart ofany million subscribers.

subscriber,v provided 1 such" connections are 1 required to be madethrough the main central oiiice shown inFigure 9. i-These operationswould'be as follows Complete the junction Ll) not shown, but thusdescribed for a mil-] lion" subscribers to earth by plug Pyoperate thecommutator thus securing control of one of the trunk lines to the maincentralsta-1 tionflfor the whole *exchangefthenby operating thecommutator three successive, times, each time making junctionfwith thcproper character upon the key boarclyaslf for example, 2,,3 cand e forsubscriber 2,5 3-4, or 99, 57 83, for'subscriber 99 57f83, w

and waiti'i 9; after each' operation for the would be called succession.

' ltis not'necessary that ineach group there I should be; fully onehundred subscribers'l when the exchange s based on a system ofjhundreds.- Likewise, -1t'i's; not necessary that one hundredsubcentral-stations should be connected to a l 7 single intermediate*central station, nor would; it bei necessary that one hundredintermediate central stations. be

c'cnnected'to agmain'central station, asthe,

exchange may bc organized-in the beginning to-accommodate the desirednumber ofsub scribers and the groups of converging lines to anycentral'station of any order be-incom plete, having perhaps but afewsetsof trunk lines or'but fewsubscribers to ia-centralQ station. The 1 deignating f numbers ,of the omitted cii'cuits. will' ofcourse be omitted,

from' thei telephoiicfdirectory, v[and the number or trunk 'lin'esreduced according I ly; It lies within my inyentioi'ifto put'intrnnkylinesifronr any cent-ralfst at ion to? any other cen'tra-l stationthat'the demands of.

